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Kenichi Yamazaki - One of the best experts on this subject based on the ideXlab platform.
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vault housed Extensometers recorded a rapid initial pulse before precursory magma reservoir inflation related to the 2011 eruption of shinmoe dake japan
Earth Planets and Space, 2020Co-Authors: Kenichi Yamazaki, Yusuke Yamashita, Shintaro KomatsuAbstract:Previous studies of the major eruption at Shinmoe-dake volcano, Japan, in January 2011 suggested that gradual injection of magma from a deep source into a shallow reservoir began in December 2009 and led to the major eruption. To investigate the initial phase of this injection event, we examined extensometer data from the Isa Observatory, ~ 18.5 km from the summit of Shinmoe-dake, and discovered a strain change event that spanned about 3 days in December 2009. The size of the strain change is comparable to those observed during each sub-Plinian eruption in 2011. The source of the rapid strain change appears to be deeper than the estimated location of the magma reservoir that directly supplied magma to the 2011 eruption sequence. These observations suggest that rapid injection of magma from the deep magmatic plumbing system in December 2009 triggered the continuous ascent of additional magma from depth, which in turn drove the climactic eruptions in January 2011. Extensometers also recorded two rapid strain change events of the same order of magnitude and with similar characteristics in December 2006 and August 2008; however, noticeable inflation of the edifice was not detected immediately following either event. This suggests that transient injection of magma into a shallow reservoir is not always followed immediately by a gradual recharge process.
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subtle changes in strain prior to sub plinian eruptions recorded by vault housed Extensometers during the 2011 activity at shinmoe dake kirishima volcano japan
Earth Planets and Space, 2013Co-Authors: Kenichi Yamazaki, Masahiro Teraishi, Kazuhiro Ishihara, Shintaro Komatsu, Koji KatoAbstract:This study focuses on strain change observations with a precision of 10−9 associated with the 2011 Shinmoe-dake eruptions in Japan, using vault-housed Extensometers installed approximately 18 km northwest of the Shinmoe-dake crater. The Extensometers recorded major strain changes of 10−7 during three sub-Plinian eruptions and subsequent magma effusion. Our analysis indicates that these extensometer records provide a reasonable estimation of the parameters of an isotropic point source that can explain eruption-related ground deformation. The Extensometers also recorded subtle strain changes of 10−9 prior to the three sub-Plinian eruptions. Time series data indicate that changes in strain at these rates are generally only observed immediately before explosive eruptions, suggesting that these strain changes are precursors to sub-Plinian eruptions. The source of these subtle strain changes is likely to be shallower than the magma chamber associated with these eruptions. The precursory strain changes might have been caused by a pressure increase and a subsequent pressure decrease under the volcano. One possible scenario that can explain these pressure changes is the accumulation of volcanic gases at depth, causing an increase in pressure that was eventually released during gas emissions from the crater prior to the explosive eruptions.
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an attempt to correct strain data measured with vault housed Extensometers under variations in temperature
Tectonophysics, 2013Co-Authors: Kenichi YamazakiAbstract:Abstract Strain data obtained by vault-housed Extensometers have precisions on the order of nanostrains, but they are distorted by variations in temperature, which cause two types of noise: “actual variations” due to the thermo-elastic effect of the Earth's crust, and “false variations” due to the thermal expansion of extensometer, which occurs when the Extensometers themselves are subjected to variations in temperature. Here, I explore a method of removing false variations, which are severe when the vault is located at shallow depths. If variations in temperature at arbitrary points inside a vault are estimated, false variations can be removed from the recorded variations in strain. I derive formulae that enable variations in temperature to be estimated at various points in a vault, based on measured variations at reference points. The formulation is valid if some simplification is allowed. I examined whether variations in temperature inside a vault can be estimated in terms of the derived formulae, and obtained the following results. When the reference temperature data are obtained from adequate points in the vault, variations in temperature at another point can be estimated with an accuracy of 0.1 °C. However, when the reference temperature data are obtained from outside the vault, estimated variations in temperature are rather inaccurate, which means that the false variations in strain cannot be removed accurately. Moreover, the data indicate that the thermal diffusivity of the ground is temporally variable, and this introduces another difficulty in correcting false variations in strain data. These results indicate that correcting the distortions in strain data due to variations in temperature is much more difficult than anticipated.
Leszek Salbut - One of the best experts on this subject based on the ideXlab platform.
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Design and testing of a low-cost full-field integrated optical extensometer
Optical Sensors 2008, 2008Co-Authors: Jerzy Krezel, Malgorzata Kujawinska, Grzegorz Dymny, Leszek SalbutAbstract:The paper deals with design and implementation of an optical extensometer based on grating (moire) interferometry, for large engineering construction monitoring. The paper presents the principles of the grating interferometry and the construction of miniaturized and portable version of grating interferometer and its implementation for out-door measurement directly at civil engineering structures. The paper presents also a concept of the low-cost full-field optical extensometer.
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Automated laser extensometer for full-field and local in-plane displacements and strain measurement
Seventh International Symposium on Laser Metrology Applied to Science Industry and Everyday Life, 2002Co-Authors: Leszek SalbutAbstract:The novel type of automated laser full-field extensometer based on grating (moire) mterferometry is presented. It is designed for medium size field of view (6 x 4.5 mm2). The extensometer is mechanically and virtually (through software) integrated with a standard loading machine. It has possibility to control the load on the base of local on-line strain measurements. It enables the measurements during static, monotonic and cyclic loads and fill-field analysis of arbitrary sequence of images. The extensometer gives high contrast and good quality interferograms and is insensitive to vibrations and works with simple, low cost laser diode. The apparatus includes very convenient fringe pattern analysis software with possibilities to design the calculation protocol best fitted to specific measurement tasks. The capabilities of the extensometer are presented on the example of low cyclic fatigue testing of steel specimens with notch.
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Novel laser full-field extensometer integrated with loading machine
Optical Diagnostics for Industrial Applications, 2000Co-Authors: Leszek SalbutAbstract:Breaking barrier of the mass production of novel materials (composite, smart, enhanced by surface layers) and introducing new technologies (laser processing, joint between nonconventional materials) pose new requirements for the industrial systems of full-field strain analysis. This quality of experimental data has to be sufficient to introduce them into numerical analysis (FEM) to perform complicated modelling of fracture mechanics, fatigue process or residual stress distribution. The experimental method, which fulfills the quality requirements, is grating interferometry. In the paper the novel type of laser full-field extensometer based on four-beam grating (moire) interferometry is presented. It is designed for medium size field of view (6 x 4.5 mm2). The extensometer is integrated and works directly on a standard loading machine with the possibility to control the load on the base of local on-line strain measurements. It enables the measurements during static, monotonic and cyclic loads and full-field analysis of arbitrary sequence of images. The Extensometers give high contrast and good quality interferograms, are insensitive to vibrations and work with simple, low cost laser diode. The capabilities of the Extensometers are presented on the example of low cyclic fatigue testing of steel specimens with hold and notch.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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New generation of optical Extensometers based on grating (moire) interferometry
Laser Interferometry X: Techniques and Analysis, 2000Co-Authors: Malgorzata Kujawinska, Leszek SalbutAbstract:Current design, analysis and control engineering applications require effective experimental methodologies and tools for determination of displacement and strain fields as well as material characterization. The quality of experimental data obtained at industrial environment has to be sufficient to introduce them into further numerical analysis by FEM (CAE) or use immediately for product quality assessment process. In the paper we present two novel types of full-field laser Extensometers based on four-beam, grating (moire) interferometry method. The first type of Extensometers is designed for medium size field of view (6 x 4.5 mm ). It is integrated and works directly on a standard loading machine with the possibility to control the load on the base of local on-line strain measurements. It enables the measurements during static, monotonic and cyclic loads and full-field analysis of arbitrary sequence of images, The second type, based on the concept of waveguide interferometer, is designed for small size field of view (min. 0.18 x 0. 12 mm2). It is integrated with a standard optical microscope and it seems to be an excellent tool for local material studies and strain analysis of microcomponents. The waveguide extensometer presented includes miniature Twyman- Green interferometer, which allows to measure out-of-plane displacements. Both Extensometers give high contrast and good quality interferograms, are insensitive to vibrations and work with simple, low cost laser diode. The capabilities of the Extensometers are presented on the example of low cyclic fatigue testing of a steel specimen and local displacement and strain investigations performed at the ferritic-austenic steel sample and silicon microbeam.
J Annala - One of the best experts on this subject based on the ideXlab platform.
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Practical Aspects of Dynamic Verification of Extensometers: Part II—Actual Examples
Journal of Testing and Evaluation, 1994Co-Authors: Fj Albright, J AnnalaAbstract:Verification and calibration of an extensometer requires operation at multiple points within the desired operating range. Whereas static calibrations observe changes in sensitivity at different levels within the transducer operating range, dynamic calibrations require duplicating that range of test levels for a range of operating frequencies. Additionally, although the static accuracy of an Extensometers is relatively independent of the test machine, dynamic accuracy was believed to be quite dependent. Test results for dynamic verification of several Extensometers are presented. The focus of the tests was to gain an understanding of the advantages and disadvantages of different methods of verification. Testing was generally in accordance with ASTM E 467, Practice for Verification of Constant Amplitude Dynamic Loads in An Axial Load Fatigue Testing Machine. Two excitation methods were used: discrete frequency and pseudo-random. Evaluation of a proposed revision to ASTM E 467 is included. Use of a computer to provide an efficient, high-accuracy method of verifying the calibration of an Extensometers was explored. Further testing is recommended to determine if Extensometers dynamic verification must be done on the actual test setup, and to what extent it is repeatable.
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Practical Aspects of Dynamic Verification of Extensometers: Part I—The Concepts
Journal of Testing and Evaluation, 1994Co-Authors: Fj Albright, J AnnalaAbstract:Material property studies frequently require the measurement of load and strain. Accurate measurement of both parameters is essential. Methods for accurate static calibration and verification of load transducers and Extensometers are well established. More recently, standard practices have been developed for the dynamic calibration of load transducers. Still in its infancy is a standard method for dynamic verification of Extensometers. Dynamic verification introduces a wide range of new issues. These encompass not only the transducer but also the conditioning electronics and actual test machine. Static calibration permits the “elimination” of nearly all dynamics, whereas dynamic verification must be done in the presence of these dynamic effects. This paper outlines the various concepts that need to be understood when performing the dynamic verification of an extensometer. Problems related to computer aided verification are emphasized, issues of aliasing and resolution in particular.
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practical aspects of dynamic verification of Extensometers part i the concepts
Journal of Testing and Evaluation, 1994Co-Authors: Fj Albright, J AnnalaAbstract:Material property studies frequently require the measurement of load and strain. Accurate measurement of both parameters is essential. Methods for accurate static calibration and verification of load transducers and Extensometers are well established. More recently, standard practices have been developed for the dynamic calibration of load transducers. Still in its infancy is a standard method for dynamic verification of Extensometers. Dynamic verification introduces a wide range of new issues. These encompass not only the transducer but also the conditioning electronics and actual test machine. Static calibration permits the “elimination” of nearly all dynamics, whereas dynamic verification must be done in the presence of these dynamic effects. This paper outlines the various concepts that need to be understood when performing the dynamic verification of an extensometer. Problems related to computer aided verification are emphasized, issues of aliasing and resolution in particular.
Feipeng Zhu - One of the best experts on this subject based on the ideXlab platform.
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High-resolution and high-accuracy optical extensometer based on a reflective imaging technique
Optics and Lasers in Engineering, 2020Co-Authors: Feipeng Zhu, Pengxiang Bai, Jin Tao, Dong LeiAbstract:Abstract Optical extensometer is a popular device for strain measurement due to its merits of non-contact measurement over a wide range of strain values compared to conventional contact measurement devices. Telecentric lens is often implemented in optical Extensometers to improve the measurement accuracy by alleviating the effect of out-of-plane motion. However, the accuracy of an optical extensometer is always limited by the gauge length, which is generally less than the resolution of a digital camera. In this study, we propose a reflective imaging technique to effectively enhance the gauge length by recording two isolated long-distance regions on the specimen using a telecentric lens. The corresponding reflective imaging device was integrated in a single apparatus in which the installation of telecentric lens was very convenient. Through precise calibration, the gauge length of proposed extensometer could be increased from 1700pixels to 7477.5pixels. The performance of the proposed extensometer is evaluated using self-heating and static tests. Furthermore, the feasibility, repeatability, and reliability of the extensometer are validated by uniaxial tensile tests on a stainless-steel specimen. Experimental results showed that the axial strains obtained using proposed method were in excellent agreement with those obtained using strain gauge, and the root mean square error of strain was below 5μe in most cases. Therefore, the proposed extensometer is highly accurate and exhibits immense potential to replace mechanical extensometer and strain gauge for determining the mechanical properties of materials.
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High-accuracy biaxial optical extensometer based on 2D digital image correlation
Measurement Science and Technology, 2017Co-Authors: Feipeng Zhu, Yan Gong, Pengxiang Bai, Zhencheng Jiang, Dong LeiAbstract:In two-dimensional digital image correlation (2D-DIC), the optical axis of the camera must be exactly perpendicular to the object surface to avoid the generation of out-of-plane displacement, which leads to low strain accuracy. In this work, we first studied the strain accuracy of a common optical extensometer when the optical axis of the camera is not perpendicular to the specimen surface. Derivation reveals that even a very small oblique angle θ will introduce a considerable strain error and that an opposite oblique angle θ generates an opposite strain error of the same magnitude. Therefore, taking the strain average of these two optical Extensometers can almost entirely eliminate such effect of non-perpendicularity, which has the same form as the optical extensometer realized by dual-reflector imaging. Because the transverse strain of a specimen is less than its axial strain, the measurement of transverse strain requires higher strain-measurement accuracy. With the aid of a self-designed right-angled apparatus, we conveniently extend this 1D extensometer to a 2D situation, which is called the biaxial optical extensometer. Uniaxial tensile tests of a stainless-steel specimen are conducted to evaluate the strain accuracy of the biaxial optical extensometer quantitatively. Experimental results show that the transverse and axial strains obtained using the proposed biaxial extensometer are in good agreement with those obtained using strain gauges and that the proposed extensometer achieves higher strain accuracy compared to the 3D-DIC extensometer.
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Optical extensometer and elimination of the effect of out-of-plane motions
Optics and Lasers in Engineering, 2015Co-Authors: Pengxiang Bai, Feipeng ZhuAbstract:Abstract A novel optical extensometer is developed to estimate the local uniform strain on planar surface accurately. The proposed system consists of a shared large format lens and two image sensors, which acquire pairs of images of two isolated small regions on the object surface simultaneously. Digital image correlation (DIC) algorithm is applied to determine the relative displacement between gauge points designated on recorded pairs of images. Then local strain can be extracted after dividing the relative displacement by the scale distance. Moreover, a special experimental setup called “correction sheet” is used to eliminate the virtual strain induced by out-of-plane motions. Uni-axial tensile experiments are performed to validate the reliability and resolution of the optical extensometer, and the measurement results demonstrate that the resolution of the optical extensometer achieves 2–3 μe.
Dong Lei - One of the best experts on this subject based on the ideXlab platform.
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High-resolution and high-accuracy optical extensometer based on a reflective imaging technique
Optics and Lasers in Engineering, 2020Co-Authors: Feipeng Zhu, Pengxiang Bai, Jin Tao, Dong LeiAbstract:Abstract Optical extensometer is a popular device for strain measurement due to its merits of non-contact measurement over a wide range of strain values compared to conventional contact measurement devices. Telecentric lens is often implemented in optical Extensometers to improve the measurement accuracy by alleviating the effect of out-of-plane motion. However, the accuracy of an optical extensometer is always limited by the gauge length, which is generally less than the resolution of a digital camera. In this study, we propose a reflective imaging technique to effectively enhance the gauge length by recording two isolated long-distance regions on the specimen using a telecentric lens. The corresponding reflective imaging device was integrated in a single apparatus in which the installation of telecentric lens was very convenient. Through precise calibration, the gauge length of proposed extensometer could be increased from 1700pixels to 7477.5pixels. The performance of the proposed extensometer is evaluated using self-heating and static tests. Furthermore, the feasibility, repeatability, and reliability of the extensometer are validated by uniaxial tensile tests on a stainless-steel specimen. Experimental results showed that the axial strains obtained using proposed method were in excellent agreement with those obtained using strain gauge, and the root mean square error of strain was below 5μe in most cases. Therefore, the proposed extensometer is highly accurate and exhibits immense potential to replace mechanical extensometer and strain gauge for determining the mechanical properties of materials.
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High-accuracy biaxial optical extensometer based on 2D digital image correlation
Measurement Science and Technology, 2017Co-Authors: Feipeng Zhu, Yan Gong, Pengxiang Bai, Zhencheng Jiang, Dong LeiAbstract:In two-dimensional digital image correlation (2D-DIC), the optical axis of the camera must be exactly perpendicular to the object surface to avoid the generation of out-of-plane displacement, which leads to low strain accuracy. In this work, we first studied the strain accuracy of a common optical extensometer when the optical axis of the camera is not perpendicular to the specimen surface. Derivation reveals that even a very small oblique angle θ will introduce a considerable strain error and that an opposite oblique angle θ generates an opposite strain error of the same magnitude. Therefore, taking the strain average of these two optical Extensometers can almost entirely eliminate such effect of non-perpendicularity, which has the same form as the optical extensometer realized by dual-reflector imaging. Because the transverse strain of a specimen is less than its axial strain, the measurement of transverse strain requires higher strain-measurement accuracy. With the aid of a self-designed right-angled apparatus, we conveniently extend this 1D extensometer to a 2D situation, which is called the biaxial optical extensometer. Uniaxial tensile tests of a stainless-steel specimen are conducted to evaluate the strain accuracy of the biaxial optical extensometer quantitatively. Experimental results show that the transverse and axial strains obtained using the proposed biaxial extensometer are in good agreement with those obtained using strain gauges and that the proposed extensometer achieves higher strain accuracy compared to the 3D-DIC extensometer.
